In process automation technology, field devices are often applied, which serve for registering and/or influencing process variables. Serving for registering process variables are sensors, such as, for example, fill level measuring devices, flow measuring devices, pressure- and temperature measuring devices, pH-redox potential measuring devices, conductivity measuring devices, etc., which register the corresponding process variables, fill level, flow, pressure, temperature, pH-value, and conductivity. Serving for influencing process variables are actuators, such as e.g. valves or pumps, via which the flow of a liquid in a pipeline section, or the fill level in a container, can be changed. A large number of such field devices are produced and sold by the firm, Endress+Hauser.
In modern industrial plants, field devices are often connected via bus systems (Profibus®, Foundation® Fieldbus, HART®, etc.) with a process control unit, which performs process control using the field devices associated with it. Besides wired communication, there is, both within a fieldbus system as well as also detached from such, the opportunity for wireless communication (e.g. communication via radio). For implementing wireless communication, newer field devices can be embodied as radio field devices. Along with that, there is the opportunity of enabling wireless communication for data of a field device by connecting to the relevant field device a wireless adapter, which has a radio unit. For example, a wireless adapter is described in WO 2005/103851 A1.
Additionally or alternatively to using a wireless adapter to enable the connecting of a field device to a wireless fieldbus, there is, furthermore, the opportunity of using a wireless adapter, in order to transmit data relative to the field device wirelessly to a corresponding communication unit, which is formed, for example, by a host. This transmission can occur especially via a long distance transmission network. In this way, for example, regularly, inventory data, which are formed e.g. by measured values of the respective field device, can be transmitted to the communication unit and managed there. For this, especially a corresponding server is implemented in the communication unit. A typical application could be, for example, that the wireless adapter, at first, predetermined times, queries measured values from the field device connected thereto. The queried measured values are, in given cases, collected in the wireless adapter. They are, at second, predetermined times, transmitted wirelessly to the communication unit. The time separation between the second, predetermined times is, especially when the measured values are collected, clearly greater than the time separation between the first, predetermined times. For example, the collected data might be transmitted to the communication unit only once a day.
Often, there is the need to operate the unit formed of field device and thereto connected wireless adapter as an autarkic unit. In this case, the field device is supplied with electric power by the wireless adapter. In order to prevent an unnecessary loading of the electrical current supply unit (e.g. single-use battery, rechargeable battery, etc.) of the wireless adapter, the wireless adapter is switched off, especially at times, when it is not communicating (especially at times other than the first and second, predetermined times). Also, the field device is supplied with electric power by the wireless adapter and turned on only when a communication with the wireless adapter is to be performed. This sporadic turning off of the wireless adapter (and also of the field device) leads, however, to a considerable time delay in the case of analysis (respectively, diagnosis) and, in given cases, in the case of error removal, in case a status change, especially an error, occurs in the field device.
A status change of the field device is reported by the field device, as a rule, (depending on fieldbus protocol) by a status, basic information report. The status, basic information report is, for example, transmitted to the wireless adapter together with a measured value of the field device. Apart therefrom, that in the field device a status change has occurred, the wireless adapter has, as a rule, no other information. As a rule, especially the collection of data continues. In the case of the transmission of the data relative to the field device to the communication unit (which occurs, for example, at the second, predetermined times) it can be provided that, in such case, also the information is included, that a status change has occurred in the field device. The communication unit is, in this way, however, informed first relatively late concerning the status change. If, for example, an error has occurred in the field device, so that the provided measured values are no longer valid and thus invalid measured values were collected by the wireless adapter over a considerable length of time. Also, is in the case of the discussed manner of operation, an analysis of the status change (diagnosis of the field device) and, in given cases, an error removal via the communication unit, especially by an application (for example, a configuration tool) accessing the communication unit, is made difficult. An accessing of the wireless adapter and, in given cases, a retrieval of additional status information from the field device, as well as, in given cases, a change of parameter settings of the field device, are made especially difficult by the fact that the wireless adapter, at times when no planned transmission of data relative to the field device takes place, is not available for communication with the communication unit. In this way, an analysis and/or error removal to be performed via the communication unit can experience a delay until the next, planned transmission of data between the wireless adapter and the communication unit. The delay can be up to a day or even longer. Furthermore, it is problematic that, in the case of a reported status change of the field device, there is not in each case a more extensive analysis and/or error removal performed. For evaluating whether, in the case of the given status of the field device, more extensive steps, such as, for example, an analysis, an error removal, etc., are required, device specific knowledge is required.